Piston-packing.



F. E. SMALL.

. PISTON PACKING.

APPLICATION FILED FEB. 2s, |915.

l l 73, 3 l 9, Patented Feb. 29, 1916.

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FREDERICK E. SMALL, 0F NEEDHAM, IVIASSACHU'SEUETS.

EPISTON-PACKING.

To all whom i may concern.'

Be it known that l, FREDERICK E. SMALL, a citizen of the United States, and resident of Needham, in the county of Norfolk and State of Massachusetts, have invented new and useful Improvements in Piston-Packings, of which the following is a specification.

This ,invention relates to piston packings and while adapted to the packing of pistons generally, it is especially designed for lthe packing of pistons of internal combustion engines. ln such engines the cylinder is cooled in operation while the piston is hot, and the latter therefore expands more than the cylinder and must fit loosely within the cylinder to avoid binding. In order to maintain the high compression which is necessary, the packing must .be tight not only between the packing and the cylinder but between the packing and the groove of the piston to prevent leakage underneath the piston rings. The packing must also be capable of accommodating `itself to inequalities in the surface of the cylinder due to wear or similar defects. A type of packings commonly used, known as snap rings, are open to many objections hereinafter referred to, and the object of the present invention is to provide piston packin'gs of this character whichwill overcome these objections.

rlhe invention consists in the novel features of construction hereinafter `described and particularly pointed out in the claims.

ln the accompanying drawings which illustrate certain embodiments of the invention,-

Figure l is a side elevation of a piston packing in place on the piston head; Fig. 2 is a similar view showing a modified form of packing; Fig. 3 is an enlarged detail view in cross section of the packing shown in Fig. 1; and Fig. t is an enlarged detail view in cross section of the acking shown in Fig. 2.

Heretofore it has 1lbeen the invariable practice so far as l am aware in the manufacture of snap packing rings, so-called, to make the ring exactly to t and fill the groove in the piston. With this construction the ring must needs be sprung over the piston all at once and snapped into the groove all at once. rlChis tends to stretch and distort the ring so that it will not make a good joint v `with the cylinder, land also frequently results in the breaking of the ring. The removal of such snap rings is attended with Specication of Letters Patent.

Patenten nen. ce, raie.

Application filed February 26, 1915. Serial No. 10,852.

even greater difficulties since there is not only the danger of distorting or breaking the ring in getting it out of the groove, but it cannot be removed at all without inserting the usual expanding strips under the ring in a manner familiar to engineers. lt has also been the practice heretofore to make snap rings of larger exterior circumference than the circumference of the cylinder; the ring is then compressed into the bore of the cylinder and the natural tendency of the ring to expand is relied upon to make tight joint with the cylinder. When such a ring is compressed into the bore of the cylinder there is a slight distortion of the ring so that it does not make a true lit, and further there is a tendency for the ring to elongate a little in the direction of the grooves in pistons, and with less likelihood of distortion or breaking; and further a structure in which thepacking ring is turned to substantially the same size as the cylinder bore, so that it will in its normal condition make a true fit with the cylinder bore and bear equally thereon at all points.

Referring to the drawings, A. represents the cylinder, P the piston, and Gr the annular groove or channel in the piston for receiving the packing rings.

inthe forms shown in Figs. l` and 3, the packing consists of a suitable ring B divided at a single point b but otherwise continuous. rlhe ring is resilient, but instead of expanding into contact with the cylinder bore by its own resiliency, it is preferably turned to substantially the same size as the cylinder bore. The cut b is preferably made on a line diagonal to the axis of the piston, and the clearance between the cut ends of the ringwhen in normal position within the cylinder is so minute that the leakage therethrough is small. Such leakage is no greater than in the case of ordinary snap packing rings. The inner side of the ring B is made with an inwardly facing bevel surface b. C is a spring follower ring divided at a single point and normally tending to expand by its own resiliency. The follower ring C is preferably made of round, drawn steel wire ground fiat on the side which bears against the side wall of groove G. One advantage of using a follower ring of this form is that the round surface which bears against the bevel surface b accommodates itself to any angle or form of bevel and does not require the nice fitting which would be necessary if a spring follower ring were used with a beveled surface formed to fit the bevel b. Furthermore, the'rounded surface ring is cheaper to make and more certain and perfect in its action than a follower ring with a beveled surface to fit the bevel. The ground fiat surface of the follower r1ng C which bearsV against the side wall of the channel G possesses the advantage that there is less likelihood of the ring wearing a groove in the side wall of the channel, and less likelihood of the ring C becoming wedged between the ring B and the wall of the channel, than if the ring C were left circular in cross section.

It should be noted that the width of the ring B is substantially less than the width of the groove Cr in the piston so that a clearance of substantial width is provided between one side of the packing ringland one sideof the groove. This enables the packing ring to be easily inserted into the groove by first inserting one end of the ringy into the groove, bending or springing the ring open slightly for that purposeand tipping the ring relatively to the axis of the piston,

and then springing the rest of the ring into the groove by following around` the ring until the whole is sprung into the groove. This operation will be facilitated by the presence of the bevel b. The ring may be removed in a similar manner by first starting oneend out of the groove, then tipping the ring a little to the axis of the piston and' following itl around until the whole ring is removed from the groove.- This method of inserting and removing the ring is made possible by having the groove substantially wider than the ring" so that the groove will receive the ring when tipped or tilted to the axis of the piston.

The follower ring C, acting on the bevel surface b', by reason of its expansion exerts a constant pressure on ring B. One component of the force tends to expand the ring B radially andl press its periphery close against the' cylinder bore, while the other component of said force tends to thrust said packing ring endwise of the piston and thereby hold it close against one side wall of groove G. Thus the packing isV maintained tight against loss of pressure both between the ring and the cylinder and also underneath the ring between the ring and the piston. y

vThe same characteristic feature consistingjin a paclng substantially narrower than the groove in the piston head and forced into close engagement with the piston and cylinder by a follower ring, is present in the modification illustrated in Figs. 2 and 4. In these figures the cylinder A, the piston P and the groove G may be substantially the same as Aalready described. Instead of a one piece packing ring however, the packing ring illustrated in these figures consists of a resilient ring'D divided at a single point but otherwise continuous and having'an L-shaped form in crss section, one flange of the L extending laterally and the other flange longitudinally of the piston. The end of the lateral flange abuts 'resilient materlal, divided at a single point e, and fitting exactly within the inner angle of the packing ring D. The ring E is arranged to break joint with the ring D and is held in joint breaking position-by a pinl d2 on ring D, projectln into the space e between the ends yof ring The laterally extending flange of the ring D Ais undercut as shown at d and the abutting surface of the ring E is similarly beveled at e to fit the' undercut surface d. The purpose of vthis construction is to prevent any part of thering E, and particularly its ends adjacent to the place e where the 'ring is divided,

from expanding into ports or depressions, y

if any, in the surface of cylinder A. In a f ported cylinder, such as the cylinder of a -two cyclegasolene engine, where the packing ring has to pass ports, it might happen? that the ends of the acking ring E would spring into a port su ciently to catch on the edge of the port, thereby breaking the ring and often damaging the-cylinder. With the construction shown in Fig. 4 the, follower spring' C tends to press the packing against the wall of the groove Gr and while held in that Eosition it will be impossible for the ring to expand onaccount of the undercut surface d of the ring D, which slightly overlaps the ring E and holds it in place. In this form of the invention there is the same advantage as already explained in respect to making the groove G wider than the combined widtli lof the packir''gLD--Ev to facilitate inserting and removlng the rings without distorting or breakingiythem.

In either form there is the further advantage that no fine fitting ,of the packings to the groove is necessary, as in the case of ordinary snap rings which exactly t their grooves, since the extent of the clearance between the side wall of the groove G r and the side of the packing is not material sojlong as the groove is sufficiently wide to 'permit the easy insertion or removal of the packing.

As no nice fitting is required, my packings may be applied to old or worn grooves, or to grooves of various sizes within reasonable ranges of considerable extent. A still further advantage of making Vthe groove wider than the packing is that a clear and free space is provided to admit steam or gas behind the rings, which aids in setting the packing by steam or gas pressure.

A two-piece packing of the type shown in Figs. 2 and 4, comprising an L-shaped ring and a filler ring, but without specifying the undercut surface d and the bevel e', and without specifying the making ofthe outer circumference of the packing the same as the circumference of the cylinder bore, constitutes the subject matter ofmy former Pat ent No. 1,129,910, dated March 2, 1915, which patent was co -pending with the present application and in which an embodiment of the invention in such two-piece packing wasl specifically claimed. f

I claim:

nular groove therein, and a packing in said groove rcomprlslng a continuous resilient packing ring divided at a single point and having a beveledsurface at its inner side,

said packing being substantially less in width than the width of said groove, whereb v a clearance is provided between one side of said packing and one side of said groove, and a spring follower ring engaging the beveled surface of the packing and one wall of the groove, adapted to urge said packing in both a radial directionA andan endwise direction on the piston against the opposite wall of the groove.

2. In combination a cylinder, a piston loose within the cylinder and having an annular groove, and a packing said groove comprising a continuous res1l1ent packing ring divided at a single point and having a outer circumference of said ring being substantiallyfthe same as that of the cylinder bore, said packing ring being substantially less in width than the width of said groove, whereby a clearance is provided between one side of said packing and one side of said the beveled surface of the packing and one wall of the groove, adapted to urge said packing in both a radial direction and an endwise direction on the piston against the opposite wall of the groove.

3. In combination, a piston having an annular groove therein, and a packing in said groove comprising a continuous resilient packing ring L-shaped in cross section and divided at a single point, said ring having a beveled surface at its inner side, a second continuous resilient packing ring divided at a vsingle point, filling the inner angle of said L-shaped ring and arranged to break joint therewith, the laterally extending ange of the L-shaped ring, which forms one side of said inner angle, being undercut to overlap the second ring and prevent the expansion of said second ring out of said inner angle, and a spring follower ring engaging the beveled surface of said L-shaped packing ring and one wall of said groove, adapted to urge said two packing rings in both a radial direction and an endwise direction on the piston against the opposite Wall of said groove.

4. In combination, a piston having an annular groove therein, and a packing in said groove comprising a continuous resilient ,packing ring L-shaped in cross section and said inner angle, being undercut to overlapk the second ring and prevent the expansion of said second ring out of said inner angle, the combined width of said rings being substantially'less than the width of said groove, whereby a clearance is provided between one side of said packing rings and one side of said groove, and a spring follower ring engaging the beveled surface of said Lshaped packing ring and one wall of said groove, adapted to urge said two packing rings in both a radial direction and an endwise direction on the piston against the opposite wall of said groove.

Signed by me at Boston, Massachusetts, this 24th day of February, 1915.

FREDERICK E. SMALL. Witnesses:

ROBERT CUSHMAN, .IOSEPHINE H. RYAN. 

